Such heating devices are used, for example, in injection molding dies. They are pushed there over a material tube with a duct for the flowable material or placed around same. The outer wall of the material tube is surrounded by the heating device, which can be removed from the material tube. Furthermore, accurate temperature monitoring is important, which is achieved in practice by providing a thermocouple as a temperature sensor, whose sensor tip is in contact with the material tube and is fixed there, for example, in a crimped sleeve, which is welded to the material tube. This concrete embodiment brings with it, furthermore, the fact that the thermocouple must pass through the heating device, e.g., in a hole prepared for this purpose in the heating device, into which the thermocouple must be inserted. An example of such a hot nozzle is known, for example, from DE 10 2008 055 640 A1.
It was found in practice that the service lives of thermocouples and heating devices, which are used in hot nozzles, are different from each other in practice. However, it is complicated, if at all possible, in the prior-art embodiments to replace a defective thermocouple of a still functioning heating device or to use a functioning thermocouple of a defective heating device in conjunction with a new heating device that is able to function.